Initial Nucleation Approach for Large Grain-Size and High-Quality Microcrystalline Silicon Active Layer in Thin Film Transistors

Abstract

High mobility and stability are critical factors for thin film transistor (TFT) device quality. These parameters are directly dependent on the crystalline structure of the active layer materials. In this paper, the early nucleation approach was performed for increasing the crystalline grain size of microcrystalline silicon (μc-Si) active layer for TFT device quality. The crystalline nucleation is delicately regulated in an intense hydrogen plasma environment using the plasma enhanced chemical vapor deposition (PECVD). When compared to μc-Si:H deposition without the nucleation approach, the crystalline volume factor of μc-Si:H increased from 60% to over 80% by using the nucleation technique. The nucleation increases the crystalline grain size by five orders of magnitude. Furthermore, the surface roughness of μc-Si:H is decreased from 13.7 to 7.1 nm. A forming-gas post-annealing treatment (≤ 400°C) is used to minimize defect density. With a low microstructural factor, thermal-treated film quality improves dramatically. Nucleation approach is to be a simple and efficient for producing high-quality TFT devices.